This invention relates to the production of a monatomic beam in which substantially all of the atoms are of a ground state and, more particularly, relates to the production of a monatomic beam of oxygen produced by photodetachment of electrons from oxygen ions in the presence of a magnetic field.
In certain test environments it is desirable to produce a beam of atoms of a particular element that are neutral in charge in the ground state. One example of such a situation is in the research surrounding the provision of a space station in low earth orbit. In order to test the reaction of materials to be utilized in the space station, it is necessary to simulate the atmospheric conditions at a height of 200 to 600 kilometers, which is typical low earth orbit altitude. It has been found by previous experiments that the atmospheric condition at such an altitutde is comprised of essentially neutral atomic oxygen with a flux of approximately 10.sup.15 atoms/cm.sup.2 -second, with an effective energy of approximately five electron volts due to spacecraft orbital speed. Previous attempts to produce neutral atomic oxygen beams have produced either beams of the required energy but with low flux rates, or beams with the required flux rate but in which the atoms were of a low energy. In either case, the beams are impure and sometimes ionic.
Many problems have arisen in previous attempts to produce neutral atomic oxygen beams in the five to eight electron volt energy, and 10.sup.15 atoms/cm.sup.2 -second flux range. Past attempts have often been based on heating molecular gases to extremely high tempratures to obtain neutral atoms with high translational velocities in order to achieve energies of five electron volts. However, this procedure results in high percentages of ionized species and also a high percentage of electronically excited-state species, which are not present at low earth orbital altitudes and which will react at different rates from the neutral species that are present at such altitudes. The ionized species can be filtered out at the exit plane of the beam apparatus to leave only the neutral atoms; however, this results in a severe loss of flux. Removing the electronically excited species is even more difficult and has been performed by quenching the excited states, using a proper mixture of inert foreign gases, such as argon or krypton. The quenching procedure, however, results in an impure beam and a loss of kinetic energy of the ground-state species. Therefore, it is an object of the present invention to provide a method and apparatus to produce a beam of atomic oxygen of neutral charge in which substantially all of the atoms are at the ground state and to provide such a beam of energy and flux density that simulates the atmospheric conditions at low earth orbital altitudes.
It is another object of this invention to provide a method and apparatus for producing monatomic beams of other elements in which the atoms are at the ground state and are of a predetermined energy.